Improvement in mariners  compasses



5.. BENT.

MARINERS' COMPASS.

No.178,98. Patented May 30,1876.

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N. PETERS, PROTO-LITHOGRAFNER, wAsmNGTOn. n. C:

UNITED STATES PATENT OFFIca SILAS BENT, OF ST. LOUIS, MISSOURI.

IMPROVEMENT IN MARINERS COMPASS ES.

Specification forming part of Letters Patent No. 178,098, dated May 30, 1876 application filed March 31, 1 875.

To all whomit may concern Be it known that I, SrLAs BENT, late of the United States Navy, and now of the city and county of St. Louis and State of Missouri, have invented a new and useful Improvement in the Mariners Compass, of which the following is a full, clear, and exact description, reference being had to the annexed drawing, making part of this specification, where-- Figure 1 represents,in avertical central section, the screw used in attaching the card to the needle; Fig. 2, a top view of the needle; Fig. 3, a side elevation of the needle; and Fig. 4, a plan of the invention, showing the needle adjusted to a variation of twenty degrees west.

Like letters indicate like parts.

In using a compass, allowance must be made for the variation of its needle from the true north point. To theimariner especially is it important that this variation be properly allowed. If improperly allowed, an error of double the variation is made, and when approaching land or in intricate seas this is a fruitful source of disaster to vessels.

Hitherto it has been customary for the navigator to-use a compass whose card is permanen tly attached to the needle, rendering it necessary to make the needed correction mentally, and as often asthe variation is applied. This mental process is not only annoying, but it is so unreliable that no navigator, not even the most experienced, is free from the dangerous mistakes it involves. j

To obviate these'difficulties, and to furnish a compasswhich in its mechanical arrangement is such that by a simple manual process the variationof the magnetic needle may be applied directly to the compass by even the most uneducated seaman, so that(until a a change occurs in the variation) the courses steered will be the true courses, the winds recorded will be the true winds, the bearings taken will be" the true bearings, and no allowance or corrections forvariation whatever will be required when working up the deadreckoning, and, above all, that in shaping courses the true bearings given by the chart are the courses to be sailed, is the object of my invention.

' Referring to the accompanying drawing, A

represents the preferable form'of the magnetic needle used, and B the card. The latter is of the ordinary kind. The needle in length corresponds with the diameter of the card, and, ateither end or pole, is provided with pointers, respectively lettered N and S; The pointers are of suitable material, and, as

shown in Figs. 2, 3, and 4, extend upwardly,

nut, constituting the support for the needle, 7

and which is preferably used to attach the card to the needle at any desired adjustment.

In operation, the card and needle are relatively adjusted by bringing the north pole of the needle to the right or left of the north point of the card until the pointer N. is at the degree, or fraction thereof, that the variation is known to be east or west of the true meridian at that locality. The card and needle are then fixed in that relative position, thus adjusting them so that while the north and south points of the card will indicate the true meridian, the needle will. lie in the direction 0f the magnetic meridian, or in that direction which is the resultant of the combined application of both the terrestrial and the local variations.

In Fig. 4 the adjustment is to a variation of and the nut G, substantially as and for the purpose set forth.

2. The combination of the magnetic needle 'A, provided with the north and south pointers N. and 8., the card B, and the nut 0, substantially as and for the purpose set forth.

3. The combination, in a mariners compass, of a suitable securing device with a card and needle, the card and needle being relatively adjustable, substantially as and for the purpose shown and specified.

SILAS BENT.

Witnesses:

Tnos; S. BOWMAN, CHAS. D. MOODY. 

